U.S. patent number 9,638,873 [Application Number 13/353,768] was granted by the patent office on 2017-05-02 for receptacle ferrule assemblies with gradient index lenses and fiber optic connectors using same.
This patent grant is currently assigned to Corning Incorporated. The grantee listed for this patent is Venkata Adiseshaiah Bhagavatula, Jeffery Alan DeMeritt, Davide Domenico Fortusini, Jacques Gollier, James Phillip Luther. Invention is credited to Venkata Adiseshaiah Bhagavatula, Jeffery Alan DeMeritt, Davide Domenico Fortusini, Jacques Gollier, James Phillip Luther.
United States Patent |
9,638,873 |
Bhagavatula , et
al. |
May 2, 2017 |
Receptacle ferrule assemblies with gradient index lenses and fiber
optic connectors using same
Abstract
A receptacle ferrule assembly for a fiber optic receptacle
connector. The receptacle ferrule assembly comprises a first lens
with first second optical surfaces and a receptacle ferrule body
having first and second ends. At least one monolithic optical
system is formed in a monolithic receptacle ferrule body and
includes a lens formed at the second end of monolithic receptacle
ferrule body and an optical surface formed at the first end of
monolithic receptacle ferrule body. The optical surface is situated
adjacent to, and mated to the second optical surface of the first
lens The monolithic optical system is configured, in conjunction
with the first lens, to define a receptacle optical pathway from
the second end of the monolithic optical system to the first
surface of the first lens. According to some embodiments the first
lens is a gradient index lens.
Inventors: |
Bhagavatula; Venkata
Adiseshaiah (Big Flats, NY), DeMeritt; Jeffery Alan
(Painted Post, NY), Fortusini; Davide Domenico (Ithaca,
NY), Gollier; Jacques (Painted Post, NY), Luther; James
Phillip (Hickory, NC) |
Applicant: |
Name |
City |
State |
Country |
Type |
Bhagavatula; Venkata Adiseshaiah
DeMeritt; Jeffery Alan
Fortusini; Davide Domenico
Gollier; Jacques
Luther; James Phillip |
Big Flats
Painted Post
Ithaca
Painted Post
Hickory |
NY
NY
NY
NY
NC |
US
US
US
US
US |
|
|
Assignee: |
Corning Incorporated (Corning,
NY)
|
Family
ID: |
45582026 |
Appl.
No.: |
13/353,768 |
Filed: |
January 19, 2012 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20120189252 A1 |
Jul 26, 2012 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61434593 |
Jan 20, 2011 |
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61441956 |
Feb 11, 2011 |
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61473305 |
Apr 8, 2011 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B
6/4293 (20130101); G02B 6/4214 (20130101); G02B
6/32 (20130101); G02B 6/4206 (20130101); G02B
6/3817 (20130101); G02B 6/02385 (20130101) |
Current International
Class: |
G02B
6/42 (20060101); G02B 6/32 (20060101); G02B
6/02 (20060101); G02B 6/38 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
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1189895 |
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CN |
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0 575 993 |
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May 2001 |
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EP |
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1 109 041 |
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Jun 2001 |
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EP |
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58099129 |
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Jun 1983 |
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JP |
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63-293510 |
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Nov 1988 |
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JP |
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2003107208 |
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Apr 2003 |
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JP |
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2009109578 |
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May 2009 |
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JP |
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WO01/11409 |
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Feb 2001 |
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WO |
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WO03/076993 |
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Sep 2003 |
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WO |
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Other References
W J. Tomlinson, "Applications of GRIN-rod lenses in optical fiber
communications systems," Applied Optics, Apr. 1, 1980, vol. 19, No.
7, pp. 1127-1138. cited by applicant .
Emkey, et al., "Analysis and Evaluation of Graded-Index
Fiber-Lenses," Journal of Lightwave Technology, vol. LT-5, No. 9,
Sep. 1987, pp. 1156-1164. cited by applicant .
Palais, Joseph C, "Fiber coupling using graded-index rod lenses,"
Applied Optics, Jun. 15, 1980, vol. 19, No. 12, pp. 2011-2018.
cited by applicant .
http:\\www.cvimellesgroit.com, "Gradient-Index Lenses". cited by
applicant .
Chanclou, et al., "Design and demonstration of a multicore
single-mode fiber coupled lens device," Optics Communications 233,
2004, pp. 333-339. cited by applicant .
Senior, et al., "Misalignment losses at multimode graded-index
fiber splices and GRIN rod lens couplers," Applied Optics, Apr. 1,
1985, vol. 24, No. 7, pp. 977-983. cited by applicant .
Gilsdorf, et al., "Single-mode fiber coupling efficiency with
graded-index rod lenses," Applied Optics, Jun. 1, 1994, vol. 33,
No. 16, pp. 3440-3445. cited by applicant .
Cusworth, et al., "Angular tilt misalignment loss at a GRIN rod
lens coupler," Applied Optics, Jun. 1, 1986, vol. 25, No. 11, pp.
1775-1779. cited by applicant.
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Primary Examiner: Hollweg; Thomas A
Assistant Examiner: El Shammaa; Mary A
Attorney, Agent or Firm: Short; Svetlana Z.
Parent Case Text
This application claims the benefit of priority under 35 U.S.C.
.sctn.119 of U.S. Provisional Application Ser. No. 61/434,593 filed
Jan. 20, 2011 and U.S. Provisional Application Ser. No. 61/441,956
filed Feb. 11, 2011 and U.S. Provisional Application Ser. No.
61/473,305 filed Apr. 8, 2011 the contents of which are relied upon
and incorporated herein by reference in their entirety.
Claims
What is claimed is:
1. A receptacle ferrule assembly for a fiber optic receptacle
connector for mating with a fiber optic plug connector having a
plug ferrule assembly with a plug optical pathway, the receptacle
ferrule assembly comprising: (i) a gradient index lens having a
first planar optical surface and a second planar optical surface;
(ii) a monolithic receptacle ferrule body having first and second
ends, with a bore formed at the first end, wherein the bore has an
end within the monolithic receptacle body and the gradient index
lens resides at least partially and closely within the bore; and
(iii) at least one monolithic optical system formed in a monolithic
receptacle ferrule body, and comprising a) a lens formed at the
second end of monolithic receptacle ferrule body, and b) an optical
surface defined by the end of the bore, the optical surface being
situated adjacent to and mated to the second optical surface of the
gradient index lens; wherein the at least one monolithic optical
system being structured, in conjunction with said gradient index
lens, to define a receptacle optical pathway from the second end of
the monolithic optical system to the first surface of the gradient
index lens.
2. The receptacle ferrule assembly of claim 1 in which the length
of the receptacle optical pathway is between 0.3 mm and 12 mm.
3. The receptacle ferrule assembly of claim 1, wherein the ferrule
body is formed from material that transmits light having a
wavelength in the range from 850 nm to 1550 nm.
4. The receptacle ferrule assembly of claim 1, further comprising a
plurality of optical fibers and a corresponding plurality of
monolithic optical systems.
5. The receptacle ferrule assembly of claim 1 wherein said gradient
index lens has a length L longer than 0.25P, wherein P is the pitch
of the gradient index lens.
6. The receptacle ferrule assembly according to claim 1 wherein:
the monolithic receptacle ferrule body has opposite back and front
ends.
7. The receptacle ferrule assembly for a fiber optic receptacle
connector according to claim 1, wherein: the monolithic receptacle
ferrule body has top and bottom surfaces and the lens is formed at
the bottom surface, and the monolithic optical system further
includes a mirror formed at the back end.
8. The receptacle ferrule assembly of claim 7, wherein said
gradient index lens has a center refractive index Nc and an edge
refractive index Ne, and 1.015Ne.ltoreq.Nc.ltoreq.1.035Ne.
9. The receptacle ferrule assembly of claim 7, wherein the lens
formed at the bottom surface includes a refractive surface with
radius of curvature and a vertex, and an active device is situated
at a distance of 0.145 mm to 0.185 mm from the vertex of the lens
formed at the bottom surface, and the radius of curvature for said
lens is 0.43 mm to 0.65 mm, and said lens has a has a conic
constant C of -12 to -18.
10. The receptacle ferrule assembly of claim 9, wherein (i) said
gradient index lens has a center refractive index Nc and an edge
refractive index Ne, and 1.015Ne<Nc<1.035Ne; and/or (ii) the
diameter of the gradient index lens is between 250 .mu.m and 600
.mu.m.
11. An assembly, comprising: the receptacle ferrule assembly of
claim 1; and an active device arranged adjacent the lens formed at
the second end of the monolithic receptacle ferrule body.
12. A connector assembly comprising: the receptacle ferrule
assembly of claim 1, wherein the gradient index lens constitutes a
receptacle gradient index lens; and a plug ferrule with a plug
gradient index lens, said plug assembly matingly engaged to the
receptacle ferrule assembly so that the plug and receptacle
gradient index lenses define an interface between the plug and
receptacle optical pathways.
13. A connector assembly comprising: the receptacle ferrule
assembly of claim 1; and a plug ferrule, said plug assembly
matingly engaged to the receptacle ferrule assembly.
14. The receptacle ferrule assembly of claim 1, wherein the
monolithic receptacle ferrule body is formed from material that
transmits light having a wavelength in the range from 850 nm to
1550 nm.
15. A receptacle ferrule assembly for a fiber optic receptacle
connector for mating with a fiber optic plug connector having a
plug ferrule assembly with a plug optical pathway, the receptacle
ferrule assembly comprising: a gradient index lens having a first
planar optical surface and a second planar optical surface; a
monolithic receptacle ferrule body having first and second ends,
wherein the first end includes a bore with a planar end, and
wherein the gradient index lens resides closely within the bore so
that the monolithic ferrule body at least partially surrounds an
outside portion of the gradient index lens; at least one monolithic
optical system formed in a monolithic receptacle ferrule body and
including a) a lens formed at the second end of monolithic
receptacle ferrule body, and b) the planar end of the bore defining
a planar optical surface that is in contact with the second optical
surface of the gradient index lens; and wherein the at least one
monolithic optical system being configured, in conjunction with
said gradient index lens, to define a receptacle optical pathway
from the second end of the monolithic optical system to the first
surface of the gradient index lens wherein the gradient index lens
has a first mating geometry and is configured to form with the
fiber optic plug connector a substantially solid-solid contact at
an interface with the fiber optic plug connector, wherein said
substantially solid-solid contact is sufficient to substantially
expel liquid from the interface such that the plug optical pathway
is optically coupled through said interface with the receptacle
optical pathway.
16. A receptacle ferrule assembly for a fiber optic receptacle
connector for mating with a fiber optic plug connector having a
plug ferrule assembly with a plug optical pathway, the receptacle
ferrule assembly comprising: a gradient index lens having a first
optical surface and a second optical surface; a monolithic
receptacle ferrule body having first and second ends, with a bore
formed in the first end, with the bore having a planar end within
the monolithic receptacle ferrule body, and the gradient index lens
disposed closely within the bore such that the monolithic ferrule
body surrounds at least an outside portion of the gradient index
lens; at least one monolithic optical system formed in a monolithic
receptacle ferrule body and including a) a lens formed at the
second end of monolithic receptacle ferrule body, and b) the planar
bore end defining an optical surface situated adjacent to and mated
to the second optical surface of the gradient index lens; and
wherein the at least one monolithic optical system is configured,
in conjunction with said gradient index lens, to define a
receptacle optical pathway from the second end of the monolithic
optical system to the first surface of the gradient index lens
wherein the first optical surface of the lens is situated a
distance of not more than 200 .mu.m from a directly opposing
optical surface of said fiber optic plug connector, such that the
plug optical pathway is optically coupled through said interface
with the receptacle optical pathway, and said distance is being
sufficient to substantially small to expel liquid from the
interface.
17. A connector assembly comprising: a receptacle ferrule assembly
comprising a receptacle gradient index lens having a first optical
surface and a second optical surface; a monolithic receptacle
ferrule body having first and second ends, with the first end
having a bore formed therein, the bore having a planar end, and
wherein the receptacle gradient lens resides at least partially and
closely within the bore; at least one monolithic optical system
formed in a monolithic receptacle ferrule body and including a) a
lens formed at the second end of monolithic receptacle ferrule
body, and b) the bore end defining an optical surface formed in the
monolithic receptacle ferrule body, the optical surface being
situated adjacent to and mated to the second optical surface of the
receptacle gradient index lens; and wherein the at least one
monolithic optical system being configured, in conjunction with
said receptacle gradient index lens, to define a receptacle optical
pathway from the second end of the monolithic optical system to the
first surface of the receptacle gradient index lens; and B) a plug
ferrule, said plug assembly matingly engaged to the receptacle
ferrule assembly, further comprising the plug ferrule assembly
having a front end configured to engagingly mate with the
receptacle ferrule assembly, the plug ferrule assembly having a
plug ferrule body supporting at least one plug gradient index lens,
the plug gradient index lens i. being optically coupled to an end
of an optical fiber, and ii. in conjunction with end of the optical
fiber defining a plug optical pathway, and iii. being supported by
the plug ferrule body; the plug gradient index lens supported by
the plug ferrule body being adjacent to and optically coupled to
the receptacle gradient index lens of the receptacle ferrule
assembly to form an optical pathway interface between the
receptacle optical pathway and the plug optical pathway.
18. The connector assembly of claim 17 wherein said assembly
satisfies at least one of the following: (i) the receptacle optical
pathway and the plug optical pathway form a telecentric optical
system; (ii) wherein the plug gradient index lens supported by the
plug ferrule body has a diameter between 250 .mu.m and 600 .mu.m;
(iii) the numerical aperture of the optical fiber is not larger
than the numerical aperture of the plug gradient index lens
supported by the plug ferrule body.
19. A connector assembly for a fiber optic connector, comprising:
(a) a receptacle ferrule assembly comprising (a) a monolithic
receptacle ferrule body having a bottom surface and a front end,
the receptacle ferrule assembly having formed therein at least one
optical system having a lens formed at the bottom surface of the
receptacle ferrule body and a mirror formed at the back end of the
receptacle ferrule body, and a planar optical surface formed within
a bore at the front end; (b) a receptacle gradient index lens
closely disposed within the bore, the receptacle gradient index
lens having a front surface and a rear surface, wherein the rear
surface is in contact with the planar optical surface within the
bore; and wherein the at least one optical system and receptacle
gradient index lens to define a receptacle optical pathway from the
bottom surface to the front surface of said receptacle gradient
index lens, and the optical pathway has a substantially right-angle
bend; and a plug ferrule having a plug ferrule body with a front
end and that supports at least one plug gradient index lens, with
the at least one plug gradient index lens in conjunction with the
plug ferrule body defining a plug ferrule optical pathway; and
wherein the receptacle and plug ferrules assemblies matingly engage
at their respective front ends to form a solid-solid optical
pathway interface between the receptacle optical pathway and the
plug optical pathway, where light crossing the solid-solid optical
pathway is either collimated, convergent or divergent.
Description
FIELD
The disclosure is directed to ferrules used in fiber optic
connectors, and in particular is directed to receptacle ferrules
having at least one monolithic lens system, and is also directed to
fiber optic connectors and connector assemblies that use such
ferrules.
BACKGROUND ART
Optical fiber is increasingly being used for a variety of
applications, including but not limited to broadband voice, video,
and data transmission. As consumer devices increasingly use more
bandwidth, it is anticipated that connectors for these devices will
move away from electrical connectors and toward using optical
connections. or a combination of electrical and optical connections
to meet the bandwidth needs.
Generally speaking, conventional fiber optic connectors used for
telecommunication networks and the like are not suitable for
consumer electronics devices. For instance, conventional fiber
optic connectors are relatively large when compared with the
consumer devices and their interfaces. Additionally, conventional
fiber optic connectors need to be deployed with great care and into
relatively clean environments, and generally need to be cleaned by
the craft prior to connection. Such fiber optic connectors are
high-precision connectors designed for reducing insertion loss
between mating connectors in the optical network. Further, though
fiber optic connectors are reconfigurable (i.e., suitable for
mating/unmating), they are not intended for the relatively large
number of mating cycles normally associated with consumer
electronic devices.
Besides operating with a relatively large number of mating/unmating
cycles, consumer electronic devices are often used in environments
where dust, dirt, liquid contaminants, and like debris are
ubiquitous. Further, consumer electronic devices typically have
size and space constraints for making connections and may not be
amenable to straight optical pathways for the fiber optic
connector. Moreover, such size and space constraints may limit the
extent of an expanded-beam optical pathway through the fiber optic
connector.
SUMMARY
An aspect of the disclosure is receptacle ferrule assembly for a
fiber optic receptacle connector. According to at least one
embodiment the receptacle ferrule assembly comprises a first lens
(e.g., a gradient index) lens with first second optical surfaces
and a receptacle ferrule body having first and second ends. At
least one monolithic optical system is formed in a monolithic
receptacle ferrule body and includes a lens formed at the second
end of monolithic receptacle ferrule body and an optical surface
formed at the first end of monolithic receptacle ferrule body. The
optical surface is situated adjacent to, and mated to the second
optical surface of the first lens (for example the second optical
surface of the gradient index lens). The monolithic optical system
is configured, in conjunction with the positive power lens, to
define a receptacle optical pathway from the second end of the
monolithic optical system to the first surface of the first lens.
Preferably the first lens has positive optical power.
According to some embodiments a connector assembly comprising a
plug ferrule assembly is matingly engaged to the receptacle ferrule
assembly.
According to some embodiments the first surface of the gradient
index lens has a mating geometry configured to form with a plug
ferrule a solid-solid contact at an interface between plug and
receptacle optical pathways, with the solid-solid contact being
sufficient to substantially expel liquid from the interface.
According to some embodiments a plug ferrule assembly is matingly
engaged to the receptacle ferrule assembly. For example, according
to some embodiments the plug ferrule assembly has a front end
configured to engagingly mate with the receptacle ferrule assembly.
The plug ferrule assembly of some embodiments includes a plug
ferrule body supporting at least one gradient index lens. The
gradient index lens of the plug ferrule assembly is: (i) being
optically coupled to an end of an optical fiber, and (ii) in
conjunction with end of the optical fiber defines a plug optical
pathway, and (iii) is supported by the plug ferrule body. The
gradient index lens supported by the plug ferrule body is situated
adjacent to and is optically coupled to the gradient index lens of
the receptacle ferrule assembly in order to form an optical pathway
interface between the receptacle optical pathway and the plug
optical pathway. According to some embodiments the numerical
aperture of the optical fiber is not larger than the numerical
aperture of the gradient index lens supported by the plug ferrule
body.
According to some embodiments first optical surface of the gradient
index lens of the receptacle ferrule assembly is situated a
distance of not more than 200 .mu.m from a directly opposing
optical surface of said fiber optic plug connector, such that the
plug optical pathway is optically coupled through said interface
with the receptacle optical pathway, and the distance between the
gradient index lens and fiber optic plug connector is being
sufficient small to substantially to expel liquid from the
interface.
According to at least one embodiment the first surface of the
gradient index lens is the front surface of the gradient index lens
and the second surface of the gradient index lens is the rear
optical surface of the gradient index lens; and the monolithic
receptacle ferrule body has top and bottom surfaces and opposite
back and front ends. The first surface of the monolithic receptacle
ferrule body is at the front end, and the lens is formed at the
bottom surface. The optical system further includes a mirror formed
at the back end, and has a substantially right-angle bend. In
addition, the optical system is configured, in conjunction with the
gradient index lens, to define a receptacle optical pathway from
the bottom surface to the front end. The front end of the gradient
index lens either (i) has mating geometry configured to form with
the plug ferrule a solid-solid contact at an interface between the
plug and receptacle optical pathways with the solid-solid contact
being sufficient to substantially expel liquid from the interface;
or (ii) s situated by a distance of not more than 200 .mu.m from
the directly opposing optical surface of the fiber optic plug
connector, so as to substantially expel liquid from the
interface.
According to some embodiments of the connector assembly, the
receptacle optical pathway and the plug optical pathway form a
telecentric optical system.
According to some embodiments a method of making ferrule assembly
comprises the steps of: (i) inserting a gradient index rod into a
bore of the ferrule body; (ii) bonding the gradient index rod to
the bore; (iii) laser cutting the gradient index rod bonded to the
bore at a predetermined length, to separate the portion of said
gradient index rod bonded to the bore from another portion of the
gradient index rod.
Additional features and advantages will be set forth in the
detailed description which follows, and in part will be readily
apparent to those skilled in the art from that description or
recognized by practicing the same as described herein, including
the detailed description that follows, the claims, as well as the
appended drawings.
It is to be understood that both the foregoing general description
and the following detailed description present embodiments that are
intended to provide an overview or framework for understanding the
nature and character of the claims. The accompanying drawings are
included to provide a further understanding of the disclosure, and
are incorporated into and constitute a part of this specification.
The drawings illustrate various embodiments and together with the
description serve to explain the principles and operation.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an isometric front-end elevated view of an example fiber
optic connector plug;
FIG. 2 is an isometric partially exploded top-down view of the
fiber optic connector plug of FIG. 1, but with the plug ferrule
sleeve removed to reveal a ferrule holder that otherwise resides
within the sleeve interior and that supports a plug ferrule;
FIG. 3 is an isometric front-end elevated view of the example plug
ferrule assembly shown in FIG. 2;
FIG. 4 is a close-up, top-down view of a portion of the plug
ferrule assembly that illustrates an example configuration where
the plug gradient index (GRIN) lens interfaces with the receptacle
gradient index lens to establish an optical pathway interface
between the plug optical pathway and the receptacle optical
pathway;
FIG. 5A is a close-up cross-sectional view of the plug ferrule
front end and plug gradient index lens as taken along the line 5-5
in FIG. 4;
FIG. 5B is similar to FIG. 5A and shows the gradient index lens
being laser processed by a laser beam, where the laser beam angle
is facilitated by the angled surface adjacent to the plug recess
endwall at the front end of the plug ferrule;
FIG. 5C is similar to FIG. 5B and further shows the receptacle
gradient index lens of the receptacle ferrule assembly interfacing
with the plug gradient index lens of the plug ferrule assembly to
form the optical pathway interface between the plug optical pathway
and the receptacle optical pathway;
FIG. 6 is an isometric side-elevated view of the example fiber
optic connector plug of FIG. 1, along with an example fiber optic
connector receptacle configured to mate with the plug to form a
fiber optic connector assembly;
FIG. 7 is an isometric front-end view of the fiber optic connector
receptacle of FIG. 6;
FIG. 8 is an isometric side-elevated view similar to FIG. 6 and
illustrates the fiber optic connector plug mated with the fiber
optic connector receptacle to form the fiber optic connector
assembly;
FIG. 9 is an isometric side-elevated view similar to that of FIG. 6
but showing the fiber optic connector receptacle attached to an
active device platform;
FIG. 10A and FIG. 10B are isometric top-side and bottom-side
elevated views of an example receptacle ferrule assembly shown
engaged with the plug ferrule assembly of FIG. 3 to form a fiber
optic connector assembly;
FIG. 11A is a schematic optical diagram of an example optical
system formed in the receptacle ferrule assembly and plug ferrule
assembly;
FIG. 11B is a schematic optical diagram of another example optical
system formed in the receptacle ferrule assembly and plug ferrule
assembly;
FIG. 12 is an isometric, top-side elevated and cut-away view of the
ferrule assembly shown in FIG. 10A, with the cross-section taken
along the line 12-12 therein;
FIG. 13 is a close-up, cross-sectional view of a portion of the
ferrule assembly of FIG. 12, showing the combined plug and
receptacle optical pathways that join at an optical pathway
interface formed by interfacing the plug gradient index lens at the
plug with the receptacle gradient index lens;
FIG. 14 is an isometric top-side elevated view of an example
receptacle ferrule assembly shown engaged with the plug ferrule
assembly of FIG. 3;
FIG. 15A is a schematic optical diagram of an example optical
system without a reflector formed by the receptacle ferrule
assembly and plug ferrule assembly;
FIG. 15B is a schematic optical diagram of another example optical
system;
FIG. 15C is a schematic optical diagram of another example optical
system;
FIG. 15D is a schematic optical diagram of yet another example
optical system;
FIG. 15E illustrates schematically a telecentric optical system,
corresponding, for example, to FIGS. 15A-15B;
FIG. 16 is an isometric, top-side elevated and cut-away view of the
ferrule assembly shown in FIG. 14, with the cross-section taken
along the line 12-12 therein;
FIG. 17 is a close-up, cross-sectional view of a portion of the
ferrule assembly of FIG. 16, showing the combined plug and
receptacle optical pathways that join at an optical pathway
interface formed by interfacing the plug gradient index lens with
the receptacle gradient index lens;
FIG. 18 is an isometric front-end view of an example plug having a
plurality of plug electrical contacts; and
FIG. 19 is a perspective front-end view of an example receptacle
having a plurality of receptacle electrical contacts that form an
electrical connection with the plug electrical contacts of the plug
of FIG. 14, when the plug and receptacle are mated.
DETAILED DESCRIPTION
The disclosure is directed to ferrules used in fiber optic
connectors, and in particular relates to ferrules having at least
one lens system. The disclosure is further directed to fiber optic
plug and receptacle connectors, and connector assemblies formed by
mating plug and receptacle connectors so that the plug and ferrule
optical pathways have a solid-solid contact interface. The
solid-solid contact interface may be Hertzian, and may also have
small gaps that are often associated with contacting extended
surfaces. The solid-solid contact interface is preferably formed by
the surfaces of two adjacent gradient index (i.e., GRIN)
lenses.
The fiber optic connectors and connector assemblies are intended to
be suitable for use with commercial electronic devices and provide
either an optical connection or both electrical and optical
connections (i.e., a hybrid connection). Exemplary plug and
receptacle ferrules are described below in the context of the
respective plug connectors and receptacle connectors used to form a
connector assembly.
The discussion below makes reference to example embodiments where
two optical fibers and two optical pathways are shown by way of
illustration. However, the disclosure generally applies to one or
more optical fibers. In examples, the plug and/or receptacle
optical pathways are expanded-beam optical pathways where the light
trajectory includes at least a portion where the light rays are not
collimated, i.e., they converge and/or diverge, and in some cases
can include a portion where the light rays are substantially
collimated.
Fiber Optic Connector Plug
FIG. 1 is an isometric front-end elevated view of an example fiber
optic connector plug assembly (hereinafter "plug") 10. Plug 10
includes a plug gradient index (GRIN) lens 154, a plug housing 14
with front and back ends 18 and 20, and a central plug axis A1.
Plug housing 14 is configured to receive a fiber optical cable 30
at back end 20. Fiber optical cable 30 includes a jacket 32 that
defines an interior 34 that contains one or more optical fibers 36,
with two optical fibers shown by way of illustration. The two
optical fibers 36 may be, for example, separate transmit and
receive fibers. In an example, a boot 35 (see FIG. 6) is used when
connecting fiber optic cable 30 to plug housing 14 at back end 20
to prevent significant bending of the fiber optical cable at or
near the housing back end. Example optical fibers 36 are multi-mode
gradient-index optical fibers.
Plug 10 includes a plug ferrule assembly 38 at plug housing front
end 18. Optical fibers 36 extend from cable 30 to plug ferrule
assembly 38, as described below. Plug ferrule assembly 38 includes
a plug ferrule sleeve 40 having an open front end 42. Plug ferrule
sleeve 40 defines a sleeve interior 46. In an example, plug ferrule
sleeve 40 is in the form of a generally rectangular cylinder so
that open end 42 has a generally rectangular shape associated with
common types of electrical connectors, such as a USB connector.
FIG. 2 is an isometric partially exploded top-down view of plug 10
of FIG. 1, but with plug ferrule sleeve 40 removed to reveal a
ferrule holder 50 that otherwise resides within sleeve interior 46
and that may extend into plug housing 14. Ferrule holder 50
includes front and back ends 52 and 54, with the back end adjacent
plug housing front end 18. Ferrule holder 50 also includes a slot
60 having a wide section 62 adjacent front end 52, and a narrow
section 64 adjacent back end 54. A detent 66 exists at front end 52
along axis A1. The purpose of detent 66 is discussed below.
The transition between the wide and narrow slot sections 62 and 64
defines ferrule holder internal wall sections 68 on either side of
axis A1 and that are generally perpendicular thereto. A generally
rectangular and planar plug ferrule 70 is slidably arranged in slot
60 in wide section 62. Plug ferrule 70 has a central plug ferrule
axis A2 that is co-axial with axis A1 when the plug ferrule is
arranged in slot 60.
FIG. 3 is an isometric front-end elevated view of the example plug
ferrule assembly 70 of FIG. 2. FIG. 4 is a close-up, top-down view
of a portion of plug ferrule front end 72 that also shows a portion
of a plug receptacle assembly, introduced and discussed below. With
reference to FIGS. 2 through 4, plug ferrule assembly 70 includes a
top surface 71, a front end 72, a bottom surface 73 and a back end
74 that define a generally flat and rectangular plug ferrule body
75. Plug ferrule assembly 70 also includes a plug gradient index
lens 154 in inside bore 94. Plug ferrule 70 also includes an indent
76 at front end 72 and centered on axis A2. Indent 76 is configured
to engage detent 66 to keep plug ferrule front end 72 from
extending beyond ferrule holder front end 52 when the plug ferrule
is disposed in ferrule holder 50. In an example, plug ferrule 70 is
a unitary structure formed by molding or by machining.
With reference to FIG. 2, first and second resilient members 82 are
arranged between respective ferrule holder internal wall sections
68 and plug ferrule back end 74 and engage respective retention
pins 78. When plug ferrule 70 is subjected to a pushing force along
its central axis A2, resilient members 82 compress against internal
walls 68, thereby allowing the plug ferrule to slide within slot 60
backward toward the internal walls. When the pushing force is
removed, resilient members expand and urge plug ferrule 70 back to
its original position at slot front end 62. In an example,
resilient members 82 comprise springs. A pushing force can arise
for example when plug 10 is inserted into and mated with a
receptacle, as discussed below.
Plug ferrule body 75 includes bores 94 that run from back end 74 to
front end 72, with a bore end 96 open at the front end. Each bore
94 is sized to accommodate an optical fiber 36 extending forward
from back end 78, and a plug gradient index lens 154 extending
backward from front end 72. For example, the bore 96 may have a
larger diameter near the front end 72, in order to accommodate the
gradient index lens. In an example illustrated in FIG. 13 and
discussed in greater detail below, bores 94 are additionally
configured to accommodate a covered section 36C of optical fiber 36
and an adjacent bare fiber section 36B that includes an end 36E.
Plug ferrule 70 is shown as configured to support two optical
fibers 36 and two plug gradient index lenses 154. Such a
multi-fiber (and optionally multi-lens) configuration is suitable
for establishing connections having transmit and receive optical
signals carried by different optical fibers. Generally, plug
ferrule 70 can be configured to support one or more optical fibers
36 and one or more plug gradient index lenses 154 by including the
appropriate number of bores 94.
With continuing reference to FIGS. 3 and 4, plug ferrule assembly
70 further includes respective recesses 150 formed in front end 72
on respective sides of axis A2. Recesses 150 also include top and
bottom slots 151 and 153 at top 71 and bottom 73, respectively. In
an example shown in FIG. 3, ferrule body 75 includes an angled
surface 105 that are angled down to sidewalls 152.
In an example, recesses 150 have different cross-sectional shapes,
such as rectangular and circular as shown in FIG. 3. The different
shapes for recesses 150 serve to define a mating orientation
between plug ferrule 70 and its corresponding receptacle ferrule,
which is introduced and discussed below.
FIG. 5A is a close-up cross-sectional view of plug ferrule 70 at
plug ferrule front end 72 as taken along the line 5-5 in FIG. 4.
FIG. 5A shows an angled surface 105 of plug ferrule body 75. Angled
surface 105 facilitates laser processing of plug gradient index
lens 154 with a laser beam LB to form plug gradient index lens
second optical surface 154S2, as shown in FIG. 5B. The laser
processing of optical fiber 36 is discussed in greater detail
below. FIG. 5C is similar to FIG. 5B and shows a front-end portion
of a receptacle ferrule, namely a receptacle guide pin 378. FIG. 5C
is discussed in greater detail below.
Fiber Optic Connector Receptacle and Ferrule Assembly
FIG. 6 is an isometric side-elevated view of plug 10, along with an
example fiber optic connector receptacle (hereinafter, "receptacle"
300) configured to mate with the plug to form a fiber optic
connector assembly 500. FIG. 7 is a close-up front-end isometric
view of receptacle 300. Receptacle 300 includes a receptacle
ferrule sleeve 340 having an open front end 342. Receptacle ferrule
sleeve 340 defines a sleeve interior 346. In an example, receptacle
ferrule sleeve 340 is in the form of a generally rectangular
cylinder so that open end 342 has a generally rectangular shape
associated with common types of electrical connectors, such as the
aforementioned USB connector. FIG. 8 is similar to FIG. 6 and
illustrates plug 10 mated to receptacle 300 to form connector
assembly 500. Plug 10 mates with receptacle 330 by plug ferrule
sleeve 40 sliding into the receptacle ferrule sleeve 340.
Receptacle ferrule sleeve 340 thus serves as a receptacle
housing.
Ferrule receptacle sleeve 340 includes a tab 347 used to attached
the sleeve to an active device platform 360, such as a circuit
board (e.g., a motherboard), as illustrated in the isometric
side-elevated view of FIG. 9. Ferrule receptacle sleeve 340 also
optionally includes latching arms 349 on top surface 341 for
securing receptacle 300 to plug 10 when the two are mated to form
connector assembly 500. Latching arms 349 are shown as having a
cantilevered configuration, but can also have other suitable
configurations.
As best seen in FIG. 7, receptacle 300 further includes a
receptacle ferrule holder 350 that resides within receptacle sleeve
interior 346 and that holds a receptacle ferrule assembly 370.
Receptacle ferrule holder 350 includes a front end 352 that
substantially coincides with ferrule receptacle sleeve front end
342 and that forms a configuration for receptacle sleeve interior
346 that compliments the configuration of plug sleeve interior 46
so that the plug and receptacle can matingly engage.
FIG. 10A and FIG. 10B are isometric top-side and bottom-side
elevated views of an example receptacle ferrule assembly 370 shown
engaged with plug ferrule assembly 70 to form a connector assembly
390. Cartesian coordinates are shown for the sake of reference.
Receptacle ferrule assembly 370 has a central receptacle ferrule
axis A3 that is co-axial with plug ferrule axis A2 when the
receptacle and plug ferrules are matingly engaged as shown.
Receptacle ferrule assembly 370 includes a gradient index lens and
a ferrule body 375 having a top surface 371, a front end 372, a
bottom surface 373, and a back end 374. Receptacle ferrule 370 also
includes arms 376 on either side of receptacle ferrule axis A3 that
define sides 377 of receptacle ferrule 370 and that give the
receptacle ferrule a squared-off U-shape.
In an example, receptacle ferrule body 375 is a unitary
(monolithic) structure formed by molding or by machining. In
another example, receptacle ferrule body 375 is formed from
multiple pieces. Also in an example, receptacle ferrule body 375 is
made of a transparent material such as a transparent resin that
transmits light 120 having an optical telecommunications
wavelength, such as 850 nm, 1310 nm and 1550 nm. In an example,
light 120 has a wavelength in the range from 850 nm to 1550 nm. An
example transparent resin is unfilled Polyetherimide (PEI), sold by
the General Electric Company under the trademarked name ULTEM.RTM.
1010, which has an index of refraction of 1.6395 at 850 nm.
Receptacle ferrule front end 372 includes receptacle gradient index
lenses 155 located on respective sides of axis A3 and that extend
parallel thereto. Receptacle gradient index lenses 155 have
respective first and second optical surfaces 155S1 and 155S2.
Receptacle gradient index lenses 155 are configured to respectively
engage recesses 150 of plug ferrule 70 so that receptacle gradient
index lens 155 first optical surfaces 155S1 make contact with or
come in close proximity to second surfaces 154S2 of plug gradient
index lenses 154. Plug ferrule front end 72 and receptacle ferrule
front end 372 are thus configured with complementary geometries so
that they can matingly engage. Gradient index lenses 154, 155 may
be manufactured, for example, from a transparent glass such as
amorphous silica containing a gradient of Germania or other
updopant. The concentration of updopant is decreased, preferably
monotonically, (for example, in a linear, stepwise, or in parabolic
manner), preferably varying smoothly from the optical axis (highest
amount) toward the edge of the lens's exterior surface to provide
the desired refractive index profile. Thus, for example, if the
gradient index lens has a circular cross-section, its refractive
index can decrease along the radius with the highest refractive
index being along the optical axis, preferably producing a
parabolic refractive index profile.
Receptacle ferrule back end 374 is in an example angled relative to
top surface 371 and includes mirrors 410 on respective sides of
axis A3, with the mirrors being aligned with receptacle gradient
index lenses 155 in the Z-direction. In an example mirrors 410 are
curved and thus have optical power. In an example, mirrors 410
comprise a curved portion of receptacle ferrule body 375, formed
for example by molding. In one example, the reflectivity of mirrors
410 derives at least in part from internal reflection within
receptacle ferrule body 375. In another example embodiment, a
reflective layer 412 is provided on the curved portions of ferrule
body 375 on back end 374 that define mirrors 410 to enhance the
reflection (see FIG. 11A, introduced and discussed below).
Reflective layer 412 is thus external to but immediately adjacent
to ferrule body 375. In an example, mirrors 410 employ both
internal reflection and reflection from the reflective layer.
However, in some exemplary embodiments the mirrors may be planar.
Furthermore, some exemplary embodiments, as described below, may
not utilize mirrors.
With reference to FIG. 10B, receptacle ferrule body 375 also
includes a recess 418 formed in bottom surface 373 and in which
reside lenses 420. Lenses 420 are aligned in the Y-direction with
respective mirrors 410. Recess 418 is used to set back lenses 420
from the plane defined by surrounding generally planar bottom
surface 373. In an example, the set back is selected to provide a
distance between lenses 420 and corresponding active devices 362.
In the present disclosure, recess 418 is considered part of bottom
surface 373.
Mirror 410 and lens 420 constitute a two-element optical system 449
in one example, which formed a monolithic optical system. FIG. 11A
is a close-up schematic optical diagram of an example optical
system 426 comprising plug optical system 426P and receptacle
optical system 426R. Receptacle optical system 426R comprises the
monolithic optical system (i.e., mirror 410 and lens 420) and the
receptacle gradient index lens (GRIN) lens 155. Plug optical system
426P comprises plug gradient index (GRIN) lens 154. Cartesian
coordinates and an angular coordinate .theta. are shown for
reference. Example dimensions for the example optical system as set
forth in Table 1 below are also included in FIG. 11A. Optical
system 426 has an object plane OP and an image plane IP, which can
be reversed depending on the direction of light travel. The terms
"object plane" and "image plane" are used loosely here to denote
the respective locations of active device 362 and optical fiber end
36E, and to indicate that light is being relayed from one plane to
the other. In FIG. 11A, the direction of travel of light 120 is
based on active device 362 being a source of light (optical
radiation), such as a Vertical-Cavity Surface-Emitting Laser
(VCSEL) that emits light 120, and optical fiber 36 receiving the
light at fiber end 36E. Optical system 426 can operate in reverse
where active device 362 is a detector and optical fiber 36 emits
light at fiber end 36E. However, one can optimize the radii and
conic constants of the lenses and the lengths and refractive index
profiles of the gradient index lenses differently for optical
system 426 when active device 362 is a detector in order to improve
(e.g., optimize) light coupling efficiency. In the cases where
fiber 36 is emitting light at fiber end 36E, in order to maximize
the collection of the emitted light, it is preferred that the
gradient-index lenses have a refractive index profile such that the
numerical aperture of the gradient-index lenses is equal to or
higher than the numerical aperture of optical fiber 36.
Note that in the example of optical system 426 shown in FIG. 11A,
two-element optical system 449 is formed as a monolithic structure
in receptacle ferrule body 375. In an example, mirror 410 and lens
420 are biconic surfaces, meaning that each has different radii of
curvature in orthogonal directions. In an example, mirror 410 and
lens 420 both have positive optical power. In another example,
mirror 410 is a planar surface.
Table 1A sets forth exemplary optical system design parameters for
a variant of optical system 426 in which the optical path is bent
by approximately 90.degree.. In the table all distance measurements
are in millimeters and angular measurements are in degrees.
For the design of optical system 426 as set forth in Table 1A,
there is no need to apply a reflective coating to mirror 410,
because efficient reflection takes place by total internal
reflection within the receptacle ferrule body 375. This assumes
that the medium surrounding the receptacle ferrule body is air and
not a material having a higher refractive index than air. With
other designs, depending on the material used to form receptacle
ferrule body 375 and the refractive index of the surrounding
medium, it may be necessary to apply a reflective coating to mirror
410 to obtain efficient reflection.
It is noted here that receptacle ferrule assembly 370 can generally
have one or more receptacle optical systems 426R, with the number
of optical systems defined by the number of optical fibers 36
supported by plug ferrule 70. It is noted that preferably,
according to the following embodiments of Tables 1A-3C, the
gradient index lenses 154, 155 have planar surface(s). These
surfaces may be oriented perpendicular to the optical axis, or be
angled with respect to the optical axis. The Optical System of
Table 1A is optimized for coupling light from the active device to
the optical fiber, to provide as much light as possible to the
fiber.
TABLE-US-00001 TABLE 1A Optical system including the receptacle
with a GRIN lens and with optical turn) Parameter (units) Value and
units Operating wavelength 850 nm Material for monolithic
receptacle Ultem 1010, refractive index = ferrule body 375 1.6395
at 850 nm Material for Receptacle GRIN lens Doped silica glass,
with parabolic 155 and Plug GRIN lens 154, and refractive index
profile refractive index data for two GRIN Refractive index at
center = 1.482 lenses at 850 nm Refractive index at edge = 1.452 at
850 nm Diameter = 0.34 mm Numerical aperture of optical source 0.22
Distance from active device 362 to 0.165 mm vertex of lens 420 Lens
420 Radius of curvature = 0.538 mm Conic constant = -15.448 Clear
aperture = 0.3 mm Distance from vertex of lens 420 to 0.35 mm
mirror/reflector 410 Mirror/reflector 410 Planar surface Distance
from mirror/reflector 410 to 0.3 mm second optical surface 155S2 of
receptacle gradient index lens 155 Length of receptacle GRIN lens
155 0.6 mm Length of Plug GRIN lens 154 1.396 mm
In an example, receptacle optical system 426R has a length L and a
width W as shown in FIG. 11A, where L is about 1 mm and W is about
0.8 mm. In an example the gradient index lens has a roughly
parabolic refractive index profile, a length L2, and diameter D,
where L2 is about 0.6 mm mm and D is about 0.34 mm. Preferably, the
gradient index lens 155 and/or 154 has a center refractive index
that is 1.015 to 1.035 times its edge refractive index. Preferably
the lens 420 has a conic constant C that is more negative than -2,
for example -12 to -18.
Another exemplary embodiment of the optical system 426 is
illustrated in FIG. 11B. This exemplary optical system is optimized
for use with an optical fiber 36 is a graded-index multimode fiber
with core diameter of 80 .mu.m and a numerical aperture (NA) of
0.29. Table 1B sets forth exemplary optical system design
parameters the optical system 426 in which the optical path is bent
by approximately 90.degree.. In the table all distance measurements
are in millimeters and angular measurements are in degrees. This
embodiment also does not need to utilize a reflective coating to
mirror 410, because efficient reflection takes place by total
internal reflection within the receptacle ferrule body 375. This
optical system of Table 1B is optimized for coupling light from the
optical fiber to the active device (i.e., receiver such as
photo-detector), to provide as much light as possible to the
receiver.
TABLE-US-00002 TABLE 1B Optical System including the receptacle
with optical turn and with receptacle GRIN lens of less than 1/2
pitch length. Parameter (units) Value and units Operating
wavelength 850 nm Material for monolithic receptacle Ultem 1010,
refractive index = ferrule body 375 1.6395 at 850 nm Material for
Receptacle GRIN lens Doped silica glass, with parabolic 155 and
Plug GRIN lens 154 and refractive index profile refractive index
data for the GRIN Refractive index at center = 1.482 lenses at 850
nm Refractive index at edge = 1.452 at 850 nm Diameter = 0.34 mm
Diameter of active area of active 60 .mu.m device 362 (photodiode)
Distance from active device 362 to 0.165 mm vertex of lens 420 Lens
420 Radius of curvature = 0.110 mm Conic constant = -2.800 Clear
aperture = 0.4 mm Distance from vertex of lens 420 to 0.35 mm
mirror/reflector 410 Mirror/reflector 410 Planar surface Distance
from mirror/reflector 410 to 0.7 mm second optical surface 155S2 of
receptacle gradient index lens 155 Length of receptacle GRIN lens
155 0.2 mm Length of Plug GRIN lens 154 1.340 mm
In an example, receptacle optical system 426R has a length L and a
width W as shown in FIG. 11B, where L is about 1 mm and W is about
0.8 mm. In an example the gradient index lens has a roughly
parabolic refractive index profile, a length L2, and diameter D,
where L2 is about 0.2 mm and D is about 0.34 mm. Preferably, the
gradient index lens 155 and/or 154 has a center refractive index
that is 1.015 to 1.035 times its edge refractive index. In this
embodiment the lens 420 has the radius of curvature of about 0.1
mm, conic constant C of -2.8, and the length of the receptacle
gradient index lens 155 is 0.2 mm.
FIG. 12 is an isometric, top-side elevated and cut-away view of the
ferrule assembly 390 of FIG. 10A, as taken along the line 12-12.
FIG. 13 is a close-up cross-sectional view of a portion of the
ferrule assembly of FIG. 12. FIGS. 12 and 13 also show a portion of
active device platform 360 that includes active device 362 in the
form of a light emitter that emits light 120. An example light
emitter device is a vertical-cavity surface-emitting laser (VCSEL).
Active device 362 may also be a detector such as a photodiode in
the case where light 120 originates at the optical fiber end of
fiber optic connector assembly 500 (FIG. 8). In the present
embodiment, a light emitter configuration for active device 362 is
shown by way of example. In an example, active device platform 360
supports one or more active devices 362 and further in an example
supports at least one light emitter and one light detector (i.e.,
photodetector). In an example, the number of active devices 362
equals the number of optical systems 426.
FIGS. 12 and 13 show an optical pathway 450 between active device
362 and optical fiber 36 and when plug 10 and receptacle 300 are
mated to form ferrule assembly 390. Optical pathway 450 includes
two main sections, namely a plug optical pathway 450P on the plug
side, and a receptacle optical pathway 450R on the receptacle side.
Plug optical pathway 450P is defined by plug gradient index lens
154 and optical fiber 36 since light 120 is guided therein. The
receptacle gradient index lens 155 resides closely within a bore
480 formed at the front end of the monolithic receptacle ferrule
body 375 so that the monolithic receptacle body surrounds an
outside portion of the receptacle gradient index lens. FIGS. 11A
and 13 show an example configuration where the back surface 155S2
of receptacle gradient index lens 155 is in contact with the bore
planar end 480P, which defines an optical surface of the monolithic
receptacle ferrule body 375. The plug and receptacle optical
pathways 450P and 450R interface at an optical pathway interface
450I where first optical surface 155S1 of receptacle gradient index
lens 155 of receptacle ferrule assembly 370 makes contact with plug
gradient index lens second optical surface 154S2. This situation
may occur when receptacle gradient index lens first optical surface
155S1 comes in contact with plug gradient index lens second optical
surface 154S2 (see, e.g., FIG. 4) or comes in close proximity
thereto. In some example embodiments, the plug gradient index lens
154 extends a short distance out from plug recess wall 152 (see
e.g., FIGS. 5B and 5C). In some example embodiments, the receptacle
gradient index lens 154 extends a short distance out from the
receptacle ferule body).
In one example, light 120 from active device 362 at object plane OP
initially travels over receptacle optical pathway 450R in the
Y-direction. Light 120 starts out as divergent and is allowed to
expand as it travels toward lens 420. The amount of light expansion
is a function of the divergence of light 120 and the distance
between active device 362 and the lens. Light 120 then encounters
lens 420, which in an example has positive optical power. Positive
lens 420 acts to bend the divergent light 120 more toward the
optical axis, which forms an expanding (diverging) light beam 120B,
i.e., light beam 120B is not collimated. Active device 362 is thus
optically coupled to receptacle optical pathway 450R. Preferably,
the active device 362 is situated at a distance of 0.1 mm to 0.6 mm
from the vertex of the lens 420.
Expanding light beam 120B proceeds from lens 420 to mirror 410,
where it is reflected substantially 90 degrees. In this example
receptacle optical pathway 450R thus includes a substantially
right-angle bend defined by mirror 410 that allows for a
substantially right-angle optical connection to active device
362.
Light beam 120C proceeds from mirror 410 through a portion of
receptacle ferrule body 375 to the planar end 480P of bore 480 and
to the second surface 155S2 of receptacle GRIN lens 155 in contact
therewith. Receptacle GRIN lens 155 acts to reduce the divergence
of the light beam. In an example the light beam is substantially
collimated when it reaches optical pathway interface 450I.
Receptacle optical pathway 450R interfaces with plug optical
pathway 450P at optical pathway interface 450I, which is defined by
first optical surface 155S1 of the receptacle gradient index lens
155 and the second optical surface 154S2 of the plug gradient index
lens 154. Light 120C thus passes directly from receptacle 300 to
plug 10 through optical pathway interface 450I.
After crossing optical pathway interface 450I the light enters plug
optical pathway 450P, which comprises plug GRIN lens 154. Plug GRIN
lens 154 acts to focus the light beam to a sufficiently small size
to allow coupling to optical fiber 36.
Preferably, the length of the receptacle optical pathway is between
0.3 mm and 12 mm, more preferably between 0.5 mm and 8 mm, even
more between 0.6 mm and 6 mm. It is also preferable that the
distance from the active device 362 to the fiber is 1 mm to 9 mm,
more preferably 1 mm to 6 mm and most preferable between 1.2 mm and
3 mm. It is also preferable that the numerical aperture (NA) of the
active device 362 is about 0.2 to 0.3 (e.g., 0.22), the numerical
aperture NA of the fiber is 0.2 to 0.3 (e.g., 0.29) that the core
diameter of the fiber be at least 30 .mu.m, preferably at least 60
.mu.m, and most preferably 75 .mu.m to 85 .mu.m (e.g., 80 .mu.m).
It is also preferable that the magnification M provided by the
optical system (source to fiber) is about 0.85 (i.e., 0.85.+-.0.15,
more preferably 0.85.+-.0.1). Preferably, the diameter of GRIN
lens(es) is between 250 .mu.m and 600 .mu.m, more preferably
between 275 .mu.m and 400 .mu.m.
To maximize the transmission of optical power from plug to
receptacle it is preferable to control both lateral (or radial)
offset and angular alignment of plug and receptacle optical systems
426P and 426R. This, for example, can be accomplished with the aid
of housings or sleeves which provide rough alignment used in
combination with features integral to the plug and receptacle
ferrule bodies for fine alignment. One can match the tolerance to
error of the optical systems with the alignments achievable in the
components providing mechanical alignment. The diameters of the
gradient index lenses affect the performance of that the optical
system because larger diameters lead to reduced sensitivity of loss
due to radial offset, but also to an increased sensitivity of loss
to errors of angular alignment or non-parallelism of optical axes.
Conversely smaller diameters provide reduced sensitivity to errors
of angular alignment but increased sensitivity of loss to radial
offset. The sensitivity to these errors can be quantified by using
optical ray-tracing to calculate the optical coupling efficiency in
the presence of alignment errors, for example using commercially
available ray-tracing computer software. Surprisingly, by using
ray-tracing to calculate the optical coupling efficiency in the
presence of alignment errors, we found that a gradient index lens
diameter D, where 280 .mu.m.ltoreq.D.ltoreq.380 .mu.m and, more
preferably 330 .mu.m.ltoreq.diameter.ltoreq.350 .mu.m provides an
ideal combination of sensitivities to radial and angular errors and
improves the overall performance of the optical system in an
optical assembly.
Table 2A sets forth example optical system design parameters for
optical system 426 as shown in FIG. 15A. In the table all distance
measurements are in millimeters and angular measurements are in
degrees.
The optical designs set forth in Tables 1A, 2A and 3A are optimized
for the direction of light from active device 362 to fiber end 36E.
The design is optimized based on the following four main
conditions: 1) optical fiber 36 is a graded-index multimode fiber
with core diameter of 80 .mu.m and a numerical aperture (NA) of
about 0.29; 2) Active device 362 is in the form of a VCSEL with a
circular active area having diameter of 10 micrometers; 3) the
operating wavelength is 850 nm; and 4) the monolithic receptacle
ferrule body 375 that realizes the two-element optical system 449
is made of the aforementioned ULTEM.RTM. 1010, which has a
refractive index n=1.6395 at the stated operating wavelength. The
plug gradient index lens 154 and receptacle gradient index lens 155
are formed of amorphous Silica and Germania so combined as to
provide a parabolic gradient of refractive index.
It is noted that the optical system designs of Tables 1A-3B can be
easily modified to provide similar performance. For example, if one
of the distances is changed, then the gradient index profile, or
the length of one or both of the gradient index lenses, or the
radius of curvature or conic constant of the lens formed at the
second end of monolithic receptacle can be changed to maintain
optical performance.
For example, in the optical system design of Table 1A, if the
distance from mirror/reflector 410 to second optical surface 155S2
of receptacle gradient index lens 155 is increased from 0.3 mm to
0.4 mm, the length of receptacle gradient index lens 155 is reduced
from 0.6 mm to 0.56 mm and the radius of curvature of lens 420 is
changed from 0.538 mm to 0.558 mm, the desired optical performance
is maintained. It is also noted that if the distance from the
vertex of lens 420 to mirror/reflector 410 is changed by a value x
and the distance from mirror/reflector 420 to second surface 155S2
of receptacle gradient index lens 155 is changed by an equal and
opposite value -x, the optical performance is essentially
unaffected.
For example, it is noted that the tolerances for the radius of
curvature and conic constant of lens 420 for the exemplary
embodiments corresponding to Tables 1A, 1B, 2A, 2B and 3A-3B is are
.+-.20%, preferably .+-.15%, more preferably about .+-.10%, and
most preferably .+-.5%. The tolerance on the distance from active
device 362 to vertex of lens 420 is, for example, .+-.20 .mu.m and
preferably .+-.10 .mu.m. The tolerance on the total distance
(measured along the direction of the optical rays) from vertex of
lens 420 to second optical surface 155S2 of receptacle gradient
index lens 155 is, for example, .+-.40 .mu.m and preferably .+-.30
.mu.m The tolerance on the length of the gradient index lenses, for
example, can be, is .+-.20 .mu.m and preferably .+-.10 .mu.m and
more preferably .+-.5 .mu.m. Also, for example, for the optical
systems of Tables 1A and 2A the distance from active device 362 to
vertex of lens 420 may be 0.145 mm to 0185 mm and the radius of
curvature for lens 420 may be 0.43 to 0.65 mm, (e.g., 0.53 to 0.55
mm). It is also noted that the optical designs can be scaled up or
down, by increasing or reducing linear dimensions (e.g., radii and
distances) by the same multiplication factor, without affecting
optical performance.
It is also noted that the length of any of the gradient lenses can
be also changed by a distance that is approximately equal to an
integer number (n) of half pitches (n.times.1/2P). For example, the
length or receptacle gradient index lens 155 can be increased by an
integer number of half pitches, thus increasing the length of
receptacle optical system 426R. In some embodiments, the length L
of the gradient index lens(s) is longer than 0.25P, wherein P is
the pitch of the gradient index lens. In some embodiments, the
length of at least one of the gradient index lenses is longer than
0.5P, wherein P is the pitch of the gradient index lens. The longer
gradient index lenses unexpectedly provide the advantage of
increasing the overall length of the optical system, thus
permitting a greater separation distance between the active device
362 and the fiber 36, without compromising the optical performance
of the system.
It is noted here again that receptacle ferrule assembly 370 can
generally have one or more receptacle optical systems 426R, with
the number of optical systems defined by the number of optical
fibers 36 supported by plug ferrule 70.
TABLE-US-00003 TABLE 2A Optical System including receptacle without
optical turn. Parameter (units) Value and units Operating
wavelength 850 nm Material for monolithic receptacle Ultem 1010,
refractive index = ferrule body 375 1.6395 at 850 nm Material for
Receptacle GRIN lens Doped silica glass, with parabolic 155 and
Plug GRIN lens 154, and refractive index profile refractive index
data for the GRIN Refractive index at center = 1.482 lenses at 850
nm Refractive index at edge = 1.452 at 850 nm Diameter = 0.34 mm
Numerical aperture of optical source 0.22 Distance from active
device 362 to 0.165 mm vertex of lens 420 Lens 420 Radius of
curvature = 0.538 mm Conic constant = -15.448 Clear aperture = 0.3
mm Distance from vertex of lens 420 to 0.65 mm second optical
surface 155S2 of receptacle gradient index lens 155 Length of
receptacle GRIN lens 155 3.272 mm Length of Plug GRIN lens 154
1.396 mm
In an example, as shown in FIG. 15A, the optical path that
corresponds to the optical system 426R has a length L and the
optical system 426R has a width W, where L is about 4.1 mm and W is
about 1.0 mm. As shown in FIG. 15, in at least an example gradient
index lens 155 has a roughly parabolic refractive index profile, a
length L2 and diameter D as shown in FIG. 15A where L2 is about 3.3
mm and D is about 0.34 mm.
Table 2B sets forth example optical system design parameters for an
optical system in which receptacle optical system 426R comprises
mirror 410 and lens 420 and includes gradient index lenses 154,
155. This optical system is illustrated in FIG. 15B. This exemplary
optical system is optimized for optimum optical coupling from the
exemplary optical fiber 36 to the active device 362 (e.g., a
receiver such as a photodetector, for example--i.e., to provide the
maximum amount of light to the active device 362. In this example
the optical fiber 36 is a graded-index multimode fiber with core
diameter of 80 .mu.m and a numerical aperture (NA) of 0.29.
TABLE-US-00004 TABLE 2B receptacle with optical turn and with
receptacle GRIN lens of more than 1/2 pitch length. Parameter
(units) Value and units Operating wavelength 850 nm Material for
monolithic receptacle Ultem 1010, refractive index = ferrule body
375 1.6395 at 850 nm Material for Receptacle GRIN lens Doped silica
glass, with parabolic 155 and Plug GRIN lens 154 refractive index
profile Refractive index at center = 1.482 at 850 nm Refractive
index at edge = 1.452 at 850 nm Diameter = 0.34 mm Diameter of
active area of active 60 .mu.m device 362 (photodiode) Distance
from active device 362 to 0.165 mm vertex of lens 420 Lens 420
Radius of curvature = 0.110 mm Conic constant = -2.8 Clear aperture
= 0.4 mm Distance from vertex of lens 420 to 0.35 mm
mirror/reflector 410 Mirror/reflector 410 Planar surface Distance
from mirror/reflector 410 to 0.7 mm second optical surface 155S2 of
receptacle gradient index lens 155 Length of receptacle GRIN lens
155 2.872 mm Length of Plug GRIN lens 154 1.340 mm
Table 3A sets forth example optical system design parameters for an
optical system, in which receptacle optical system 426R comprises
mirror 410 and lens 420 and does not comprise a gradient index
lens. This system is illustrated schematically in FIG. 15C.
TABLE-US-00005 TABLE 3A The optical system including the receptacle
with optical turn and without the receptacle GRIN lens Parameter
(units) Value and units Operating wavelength 850 nm Material for
monolithic receptacle Plastic (Ultem 1010), refractive ferrule body
375 index = 1.6395 at 850 nm Material for Plug GRIN lens 154 Doped
silica glass, with parabolic refractive index profile Refractive
index at center = 1.482 at 850 nm Refractive index at edge = 1.452
at 850 nm Diameter = 0.34 mm Numerical aperture of optical source
0.22 Distance from active device 362 to 0.6 mm vertex of lens 420
Lens 420 Radius of curvature = 0.375 mm Conic constant = -3 Clear
aperture = 0.5 mm Distance from vertex of lens 420 to 0.35 mm
mirror/reflector 410 Mirror/reflector 410 Planar surface Distance
from mirror/reflector 410 to 0.75 mm optical surface formed at
first end of monolithic receptacle ferrule body Length of Plug GRIN
lens 154 1.38 mm
Table 3B, below, sets forth an example optical system design
parameters for an optical system shown in FIG. 15D. In this
exemplary optical system the receptacle optical system does not
include a gradient index lens. The optical system of this
embodiment is optimized for coupling light from the optical fiber
to the active device.
TABLE-US-00006 TABLE 3B Parameter (units) Value and units Operating
wavelength 850 nm Material for monolithic receptacle Ultem 1010,
refractive index = ferrule body 375 1.6395 at 850 nm Material for
Plug GRIN lens 154 Doped silica glass, with parabolic refractive
index profile Refractive index at center = 1.482 at 850 nm
Refractive index at edge = 1.452 at 850 nm Diameter = 0.34 mm
Diameter of active area of active 60 .mu.m device 362 (photodiode)
Distance from active device 362 to 0.165 mm vertex of lens 420 Lens
420 Radius of curvature = 0.110 mm Conic constant = -2.800 Clear
aperture = 0.4 mm Distance from vertex of lens 420 to 0.35 mm
mirror/reflector 410 Mirror/reflector 410 Planar surface Distance
from mirror/reflector 410 to 0.9 mm optical surface formed at first
end of monolithic receptacle ferrule body Length of Plug GRIN lens
154 1.540 mm
FIG. 16 is an isometric, top-side elevated and cut-away view of the
ferrule assembly 390 of FIG. 14, as taken along the line 12-12.
FIG. 17 is a close-up cross-sectional view of a portion of the
optical connector of FIG. 16. FIGS. 16 and 17 also show a portion
of active device platform 360 that includes active device 362 in
the form of a light emitter that emits light 120. An example light
emitter device is a vertical-cavity surface-emitting laser (VCSEL).
Active device 362 may also be a detector such as a photodiode in
the case where light 120 originates at the optical fiber end 36E of
plug ferrule assembly 70. In the present embodiment, a light
emitter configuration for active device 362 is shown by way of
example. In an example, active device platform 360 supports one or
more active devices 362 and further in an example supports at least
one light emitter and one light detector (i.e., photodetector). In
an example, the number of active devices 362 equals the number of
optical systems 426.
FIGS. 16 and 17 show an optical pathway 450 between active device
362 and optical fiber 36 and when plug 10 and receptacle 300 are
mated to form ferrule assembly 390. Optical pathway 450 includes at
least two sections, namely a plug optical pathway 450P on the plug
side, and a receptacle optical pathway 450R on the receptacle side.
Plug optical pathway 450P is formed by optical fiber 36 and plug
gradient index lens 154. The plug and receptacle optical pathways
450P and 450R interface at an optical pathway interface 450I where
receptacle gradient index lens first optical surface 155S1 of
receptacle ferrule assembly 370 makes contact with plug gradient
index lens second optical surface 154S2. This may occur when the
first optical surface 155S1 of the receptacle gradient index lens
comes in contact with the second optical surface 154S2 of the plug
gradient index lens (see, e.g., FIG. 4) or comes in close proximity
thereto.
In one example, light 120 from active device 362 at object plane OP
initially travels over receptacle optical pathway 450R. Light 120
starts out as divergent and is allowed to expand as it travels
toward lens 420. The amount of light expansion is a function of the
divergence of light 120 and the distance between active device 362
and the lens. Light 120 then encounters lens 420, which in an
example has positive optical power. Positive lens 420 acts to bend
the divergent light 120 more toward the optical axis, which forms
an expanding (diverging) light beam 120B, i.e., light beam 120B is
not collimated. Active device 362 is thus optically coupled to
receptacle optical pathway 450R.
Light beam 120B proceeds through a portion of receptacle ferrule
body 375 to second optical surface 155S2 of receptacle gradient
index lens 155. Receptacle GRIN lens acts to reduce the divergence
of the light beam. In one example the light beam is substantially
collimated when it reaches optical pathway interface 450I. In some
example (See, for example, Table 1A), the receptacle gradient index
lens may have a length which is less than 1/4 pitch (less than
0.25P), for example between 0.05P and 0.25P. In a further example,
the receptacle gradient index lens may have a length which is
greater than 1/4 pitch (greater than 0.25P), for example 0.5P or
longer. Preferably the length of the gradient index lens is less
25P, for example less than 10P, for example less than 3P. As
described herein "quarter-pitch" (i.e., 1/4 pitch) length of a
gradient index lens is the length of gradient index medium in which
a substantially collimated bundle of rays is substantially focused
to a point by the guiding action of the refractive index gradient.
It will be understood that the length of the gradient index lens
may also be chosen to be less than 1/4 pitch or equal to 1/4 pitch.
Receptacle optical pathway 450R interfaces with plug optical
pathway 450P at optical pathway interface 450I, which is formed by
the first optical surface 155S1 of the receptacle gradient index
lens 155 and second optical surface 154S2 of the plug gradient
index lens 154 second optical surface 154S2. Light thus passes from
receptacle 300 to plug 10 through optical pathway interface
450I.
After crossing optical pathway interface 450I the light enters plug
optical pathway 450P, which comprises plug GRIN lens 154 and
optical fiber 36 Plug GRIN lens 154 acts to focus the light beam to
a sufficiently small size to efficiently couple light to optical
fiber 36.
The example designs set forth in Table 1A, 2A, and Table 3A are
telecentric, in the sense that light rays departing the object
plane OP in a direction parallel to the local axis reach the image
plane IP in a direction substantially parallel to the local optical
axis independent of any lateral displacement of the source (e.g.,
the active device). The telecentricity is advantageous, because it
enhances the light coupling efficiency when the optical source is
laterally misplaced from the optical axis and may result in looser
manufacturing tolerances. FIG. 15E is a schematic diagram of a
telecentric optical system. The source of the rays in FIG. 15E
represents an optical source (for example an active device) that is
laterally displaced from the optical axis by a distance dy. The
principal ray departing the source in the direction parallel to the
local optical axis reaches the image plane IP at a displacement dy'
from the local optical axis, and forming an angle .beta. wth the
normal to the local optical axis. The ratio dy'/dy represents the
optical magnification of the system. In an ideally perfect
telecentric system, the angle .beta. is 90.degree.. For example,
the optical system is telecentric if the angle
.beta.=90.degree..+-.arcsin(NA/5), and preferably
.beta.=90.degree..+-.arcsin(NA/10)], where NA is the numerical
aperture of the optical fiber. Applicants discovered that when the
angle .beta.=90.degree..+-.arcsin(NA/5), it is sufficiently close
to 90.degree., so that its difference from 90.degree. does not
substantially degrade the coupling efficiency to an optical fiber
located at the image plane (whose axis is generally parallel to the
local optical axis of the optical system). Preferably,
magnification M (M=dy'/dy) is about 0.7 to 0.9. This magnification
provides the following advantage: it is sufficiently small that, if
the optical source (such as active device 362) is laterally
displaced, the consequent lateral displacement of the image of the
optical source formed on the fiber is small such that the optical
coupling to the fiber is not significantly degraded. At the same
time, this magnification is not excessively small (an excessively
small magnification would result in rays reaching the optical fiber
with a convergence angle exceeding the acceptance angle of the
fiber, which would result in degraded coupling)
It is noted that for embodiments involving multiple optical fibers
36, there are multiple optical pathways 450. The example,
configurations for plug 10 and receptacle 50 are described by way
of illustration (see, for example FIGS. 10A, 10B, 12, 14 and 16)
using two optical fibers 36 and thus two optical pathways 450.
As discussed above, optical pathway interface 450I is formed by
receptacle gradient index lens 155 of receptacle ferrule 370
contacting or being in close proximity (less than 200 um,
preferably less than 100 um, and even more preferably less than 50
um) to plug gradient index lens 154, when plug 10 and receptacle
300 are engaged, for example providing solid-solid contact at the
optical pathway interface. This means that there is essentially no
air space the surfaces of the two gradient index lenses at optical
pathway interface 450I. In an example, receptacle gradient index
lens 155 may provide the solid-solid contact by contacting plug
gradient index lens 154 with a small amount of space (less than 200
.mu.m) between he surfaces of the two gradient index lenses.
This optical pathway interface 450I, when the distance between the
two gradient index lenses 155, 154 is small (less than 200 .mu.m),
or when the gradient index lenses 155, 154 form solid-solid
interface is advantageous because it prevents viscous liquid, dust,
dirt, debris or the like making its way into optical pathway 450.
Such contamination can substantially reduce the optical performance
of connector assembly 500 formed by mating plug 10 and receptacle
300. If fluid contaminants such as water or oil are present on
optical pathway interface 450I, the adverse effects of fluid
contaminants on optical performance are generally mitigated. This
is because any fluid contaminant that makes its way into optical
pathway interface 450I is squeezed between receptacle gradient
index lens 155 and plug gradient index lens 154 and essentially
becomes a very thin portion of optical pathway 450. Since the
contaminant is squeezed to a very thin layer, any optical losses
caused by absorption or scattering in the contaminant are reduced.
The compressed contaminant does not substantially contribute to
Fresnel losses because it is squeezed between two solid faces,
i.e., there is essentially no air interface to give rise to the
kind of substantial refractive index transition needed for
significant Fresnel reflections to occur. It is noted that the
optical designs of Tables 1B, 2B and 3B are not telecentric.
Laser Processing of Optical Fibers and Gradient Index Lenses
As discussed above briefly in connection with FIG. 5C, gradient
index lenses 154 and 155 and optical fiber ends 36E may be formed
by laser processing. Angled surface 105 at plug recess endwall 152
facilitates this laser processing because the laser beam LB can be
brought in at an angle other than 90 degrees relative to plug
ferrule top surface 71. Thus, angled surface 105 aids in the
manufacturing of plug 10 by providing relief that reduces the
chance of marking and/or damaging plug ferrule 70 with laser beam
LB. Angled surface 105 reduces the chances of laser beam LB
interacting with debris during the fiber cutting and/or polishing
process. Further, the insertion of the gradient index lenses to a
controlled depth facilitates laser cutting of the gradient index
lenses to a precise length. In some examples, the length of plug
gradient index lens 154 is cut to a single quarter pitch plus any
integer multiple of half pitches. The corollary procedure and
method for use in laser processing of the receptacle gradient index
lens 155 can be performed in a similar manner.
Angled surface 105 can have any suitable angle and/or geometry such
as between 30 degrees to 45 degrees relative to vertical (i.e., a
straight up and down), but other suitable angles/geometry are also
possible. Further, angled surface 105 can have any configuration
that preserves dimensions and structural integrity of plug ferrule
70 while also allowing for the formation of optical pathway
interface 450I. In other variations, angled surface 105 can also be
optionally recessed backward from plug recess endwall 152. By way
of example, a shoulder can be formed adjacent angled surface 105,
thereby permitting the angled surface to be recessed. For instance,
the resultant shoulder can have a depth of about 2 microns or
greater from the vertical portion of the sidewall.
In one example the steps of forming a receptacle ferrule assembly
comprise inserting a graded index rod of indeterminate length into
bore 90 of the receptacle ferrule body which has been pre-loaded
with an adhesive of refractive index intermediate between the
refractive index of the receptacle ferrule body and the graded
index material and proceeding to cause the glue to hold the
gradient index rod in place by for example the application of
ultraviolet energy to initiate cross-linking as is common with many
optical adhesives. In a further step, the precursor assembly thus
formed is, by way of example, mounted in a fixture which locates
the gradient index rod so that upon impingement of laser beam LB,
the gradient index rod thus held it is cut off at a precise length
(or fraction of pitch lengths) so as to form in one step a
receptacle ferrule assembly.
Thus, in one example, forming a ferrule assembly includes cutting
and/or polishing the one or more gradient index lenses with laser
beam LB in one or more processing steps. For instance, separate
steps may be used for cutting and polishing optical fibers 36 with
laser beam LB, but cutting and polishing may also occur in one
step. Any suitable type of laser and/or mode of operation for
creating laser beam LB can be used. By way of example, the laser
(not shown) that generates laser beam LB may be a CO.sub.2 laser
operating in a pulsed mode, a continuous-wave (CW) mode, or other
suitable mode. By way of further example laser beam LB may be moved
across gradient index lens 154 or 155 by the motion of a mirror
mounted on a galvanometer or alternatively by the motion of the
gradient index lenses through an essentially stationary laser beam.
The angle between laser beam LB and the optical fiber 36 being
processed may also be adjusted to produce the desired angle at the
fiber or gradient index lens end 36E, such as 12 degrees, 8
degrees, or flat.
Plug-Receptacle Connector Configurations
Plug 10 and receptacle 300 have complementary configurations that
allow for the plug and receptacle to matingly engage while allowing
a user to make a quick optical or hybrid electrical and optical
contact therebetween. More specifically, in an example, plug
ferrule 70 and receptacle ferrule 370 are formed such that plug 10
and receptacle 300 have respective USB connector configurations, as
shown for example in FIG. 6 and FIG. 8. Other connector
configurations for use in commercial electronic devices are also
contemplated herein and can be formed by suitably configuring plug
and receptacle ferrules 70 and 370 and their respective ferrule
holders 50 and 350.
While plug and receptacle ferrules 70 and 370 have been described
above with regard to their ability to support respective plug and
receptacle optical pathways 450P and 450R, plug ferrule 70 and
receptacle ferrule 370 can also be configured to support electrical
connections and corresponding electrical pathways as well, thus
providing for a hybrid electrical-optical connection.
FIG. 18 is a front-end isometric view of an example plug 10 that
includes plug electrical contacts 520P supported by plug ferrule
holder 50. FIG. 19 is a front-end perspective view of an example
receptacle 300 that includes corresponding receptacle electrical
contacts 520R supported by receptacle ferrule holder 350. Plug and
receptacle electrical contacts 520P and 520R form an electrical
connection between plug 10 and receptacle 300 when the plug and
receptacle are mated. Example electrical contacts may be molded
with plug and receptacle ferrules 70 and 370 so that they are
relatively flush with a wiping surface of their corresponding
ferrules (i.e., the horizontal surface of the ferrule that includes
the electrical contacts), or have other suitable attachment
means.
Although the disclosure has been illustrated and described herein
with reference to preferred embodiments and specific examples
thereof, it will be readily apparent to those of ordinary skill in
the art that other embodiments and examples can perform similar
functions and/or achieve like results. All such equivalent
embodiments and examples are within the spirit and scope of the
disclosure and are intended to be covered by the appended claims.
It will also be apparent to those skilled in the art that various
modifications and variations can be made to the present invention
without departing from the spirit and scope of the same. Thus, it
is intended that the present invention cover the modifications and
variations of this invention provided they come within the scope of
the appended claims and their equivalents.
* * * * *